DE3889911T2 - ELECTRIC BRAKE AND AUXILIARY ACCELERATION DEVICE FOR VEHICLES. - Google Patents

Description

[TECHNICAL BACKGROUND]

This invention relates to an electric braking and auxiliary motor mechanism that performs braking and auxiliary acceleration for motor vehicles and, more particularly, to an electric braking and auxiliary motor mechanism that includes a rotary machine directly coupled to the crankshaft of an internal combustion engine that drives the axle of the vehicle.

[STATE OF THE ART]

The progress of internal combustion engines, particularly improvements in supercharging technology together with the development of thermally resistant materials, have successfully realized an internal combustion engine of small displacement with high output power. However, with smaller capacity of the internal combustion engine, the effect of an exhaust retarder or an engine brake is reduced according to its displacement, which requires the simultaneous use of a retarder. More specifically, an auxiliary braking system is necessary in addition to the friction braking system mounted on the wheels to counteract acceleration induced when the motor vehicle is traveling downhill or to reduce the speed to a predetermined level in the initial stage of braking at high speed. A retarder according to an eddy current principle of a power generator has been provided with an inductor type structure directly coupled to the rotor shaft of the internal combustion engine. Although the retarder of an eddy current system is strong enough to withstand the external forces caused by irregular vibrations of the wheels due to bad roads, the system can regenerate unusable energy because all the mechanical energy consumed for braking is converted into thermal energy and released into the atmosphere. This contradicts the recent trend of improving fuel economy, and a device with a high thermal capacity mounted on a motor vehicle for thermal radiation increases inappropriately the dimensions of the system.

It has been found that the direct coupling of an inductor alternator to the crankshaft of an internal combustion engine is effective as an auxiliary retarder. It has also been found that in this system, mechanical energy consumed for braking can be converted into electrical energy and that electrical energy can be recovered in a rechargeable battery which can be used for the starter or other devices provided on the vehicle. However, a generator of this type requires improvement in that the air gap between the stator and the rotor of the generator must be as small as possible to avoid magnetic leakage flux which deteriorates the efficiency and that the manufacturing accuracy of the rotor and stator must be extensively improved. This requires considerable working experience in mass production.

The machine would be able to provide additional operating modes for the driver to improve driving performance when the start/acceleration and hill climbing/steady driving power means are used in addition to the main power means.

The inventors have carried out experiments using a multiphase squirrel cage induction machine as above, and have found that a high braking force is obtained, that electric energy generated during braking can be recovered to a large extent in a rechargeable battery, and that the rechargeable battery can be effectively used as an electric power source for auxiliary power.

The inventors conducted various experiments to understand the relationship between the rotational speed of the rotor and the braking torque transmitted to the crankshaft. They found a phenomenon in which no braking torque is generated when the rotational speed of the rotor is at a certain high value and when a low resistance value of a parallel resistor is connected to the electrical output of the machine to obtain a high braking torque. They conducted their experiments by varying the resistance value of the resistor and the rotational speed to find out the reason. They found that the braking torque decreases rapidly, when the output is terminated with a small value resistor and when the shaft speed is low, and that as the resistance value increases, the range for generating a normal braking torque is extended with higher shaft speed. However, a high braking torque cannot be achieved with a high resistance value because its dissipated energy is low.

The inventors considered the following: The multiphase squirrel cage induction machine and the inverter can be regarded as an integral DC power source. The power generated by the power source is proportional to the rotational speed of the multiphase squirrel cage induction machine, and the output voltage of the DC power source is also proportional to the rotational speed. However, the power radiated through the resistance which constitutes the load of the power source is proportional to the square of the output terminal voltage. Accordingly, when the rotational speed increases and when the output voltage increases, the radiated power exceeds the generated power. This means that the multiphase squirrel cage induction machine does not operate as a power generator in this state and that the machine rapidly loses the braking torque.

The inventors also observed that when a large electric current is continuously supplied to the resistor to continuously generate a large braking torque, the braking torque becomes smaller with the passage of time. This is because the resistor is heated by the current and because the value of the resistance increases with temperature. This means that the radiated electric energy becomes smaller. To avoid this phenomenon, a resistor with a small resistance value could be selected, but this should be avoided because the small resistance value would result in an increase in current and the stator winding of the machine would be heated when a high braking torque is generated.

On the other hand, it is known that a technique was disclosed by Volkswagen AG in West Germany in OS No. 2943554 (open patent application in West Germany) and in United States Patent No. 4,533,011, in which an electric machine as a generator used for the brake or as a motor for the auxiliary drive.

In the above patent disclosure, it is disclosed that an electric machine is connected to the crankshaft and that the electric machine is used as an auxiliary motor. It is also disclosed that the machine can be driven by an internal combustion engine as a power generator for charging the battery, the power of which is usable for the auxiliary motor. It should be noted, however, that a second clutch is provided in the disclosed device for coupling the rotor shaft of the squirrel cage induction machine to the axle of the motor vehicle and for disconnecting it from the crankshaft of the internal combustion engine. When the second clutch is opened, the motor vehicle can be driven as an electric vehicle with the auxiliary power alone to achieve a noiseless machine without air-polluting exhaust gas. However, it is not mentioned that the machine is usable as a retarder to assist the engine braking. Moreover, they do not mention anything about using a resistor with a low value for energy radiation.

JP-A-61-154462 discloses an electric motor generator mounted on the crankshaft of an internal combustion engine. Separate motor and generator coils are provided on the rotor, connected to a commutator and slip rings respectively. A single winding is carried by the stator.

JP-U-53-49608 describes an inverter circuit for an electrical machine. The circuit comprises switching elements that are controlled according to the speed of the electric machine.

DE-A-24 36 546 describes an auxiliary drive for a vehicle. Two electric machines are coupled to drive shafts of the vehicle to provide additional torque at low speeds. Energy recovered when the vehicle is braked is stored in a flywheel.

CH-A-492 336 describes an electrical braking process for an electric motor. The energy generated by braking the motor is converted into resistors.

The primary objective of this invention is to provide an auxiliary machinery system for automotive vehicles that is mechanically durable, produces little noise, enables stronger braking, and is suitable for mass production.

The second object of this invention is to provide an auxiliary machine system for automotive vehicles provided with an inverter means having a sufficient frequency range for output frequencies corresponding to changes in the rotational speed of the magnetic field of the multiphase squirrel cage induction machine so that it can be operated as an auxiliary drive means at a low cost without taking up additional space on the automotive vehicle.

The third object of the invention is to provide an auxiliary machine system for motor vehicles which can maintain a high braking torque by converting the electrical energy continuously into the resistance.

The fourth object of the invention is to provide an auxiliary machine system for automotive vehicles that can efficiently recycle electric energy generated by braking to a rechargeable battery that can be used as an auxiliary power source.

The fifth object of the invention is to provide an auxiliary machine system for automotive vehicles which can efficiently generate a high braking torque for a long period of time over a wide range of rotational speeds of the crankshaft of an internal combustion engine.

According to the present invention there is provided an electric brake and auxiliary motor mechanism for a motor vehicle having a rotary electric machine coupled to the crankshaft of an internal combustion engine for driving the axle of the vehicle, which is characterized in that the crankshaft and the rotary shaft of the rotary machine are directly coupled, that the rotary machine is a multiphase squirrel cage induction machine, that an electrical means is provided for inducing a rotary magnetic field for the multiphase squirrel cage induction machine, and that the mechanism comprises a DC power source including a rechargeable battery and an inverter that supplies a circulating magnetic field to the multiphase squirrel cage induction machine, the electric current being supplied from the DC power source, the inverter having a frequency adjustment range for enabling outputs at a frequency corresponding to the speed of the circulating magnetic field that is higher than that of the multiphase squirrel cage induction machine and a frequency corresponding to the speed of the circulating magnetic field that is lower than that of the speed but in the same direction.

This system is preferred in its structure where the rotor of the multiphase squirrel cage induction machine is mounted on a flywheel connected to the crankshaft of the internal combustion engine, while a stator of the same is mounted inside the flywheel housing.

It becomes possible to perform braking suitable for the running conditions of automobiles by directly coupling the rotor of the multiphase squirrel cage induction machine to the crankshaft of the internal combustion engine as mentioned above and electrically controlling the rotational speed of the magnetic field on the stator of the multiphase squirrel cage induction machine. More specifically, the multiphase squirrel cage induction machine can be operated as a power generator by making the rotational speed of the magnetic field smaller than the mechanical rotational speed of the rotor, thereby transmitting braking torque to the automobile. The multiphase squirrel cage induction machine can be used as a drive motor by making the rotational speed of the magnetic field higher than the mechanical rotational speed of the rotor, so as to transmit an auxiliary driving force to the crankshaft of the internal combustion engine.

Since it is impossible to predict the operating conditions for the motor vehicle which will require braking, this need always arises unexpectedly. It is therefore preferred that a rechargeable battery is initially charged with less than the specified charging capacity and that the battery be available for charging with electrical energy with high efficiency when such electrical energy is generated for electrical braking. charged energy can be used as auxiliary driving force for saving the fuel consumption of the internal combustion engine by the relevant amount.

Preferably, the inverter means according to this invention is connected between the phase terminals of the multiphase squirrel cage induction machine and the two terminals of the DC power source and is provided with switching elements, each of which comprises a parallel circuit of transistors and diodes.

It may also comprise a rotating sensor which detects the rotational speed of the multiphase squirrel cage induction machine as an electrical signal, a control means which generates control references during the time the vehicle is driven, an adder which outputs control signals for supplying the sum to the switching elements by adding the control reference to the rotational speed data, a series circuit comprising a switching circuit and a resistor with a small resistance value connected to both terminals of the DC power source.

Preferably, the control means for providing the reference for control comprises: a switch manipulated by the driver of the car for commanding auxiliary acceleration, another switch manipulated by the driver for commanding auxiliary deceleration, and a programmed control circuit which generates the control reference for inducing a different slip in positive or negative values for the multi-phase squirrel cage induction machine by manipulating the two switches. It is preferred that the control means for providing the reference comprises a circuit which inputs the manipulation information of the start key switch of the internal combustion engine and also that the programmed control circuit comprises means for generating the reference so as to induce a circulating magnetic field suitable for starting the internal combustion engine by means of the multi-phase squirrel cage induction machine based on the above information.

The DC power source may comprise a rechargeable battery having a nominal terminal voltage lower than the nominal terminal voltage the DC power source, with a step-up chopper and a reactor type step-down chopper connected to the rechargeable battery. The switching circuit may comprise a circuit which is automatically closed when the terminal voltage of the DC power source reaches a predetermined voltage higher than the nominal terminal voltage thereof.

The mechanism of this invention thus constructed can be used as a braking system when the rotational speed of the rotating magnetic field is controlled to achieve a negative slip with respect to the rotational speed of the rotor, thus operating as a power generator, and can be used as an auxiliary motor when it is controlled to achieve a positive slip with respect to the rotational speed of the rotor.

Since switching elements of a complicated type comprising a parallel connection of transistors and diodes are installed in the inverter circuit, the direct current electric power can be taken from the elements when the mechanism is used as a generator, and the electric power for the circulating magnetic field can be supplied from the direct current power source through these elements when used as a motor. The speed information of the multiphase squirrel cage induction machine is detected in the form of electric signals, with which negative feedback control is carried out to supply the desired circulating magnetic field to the induction machine through the control of the inverter circuit. This enables control with higher stability and higher accuracy. The control reference for the negative feedback control is generated in accordance with the operating conditions so as to adapt to the conventional driving conditions of the motor vehicle.

When the multi-phase squirrel cage induction machine is used as a generator, the generated energy can be recycled for the DC power source. However, it is impossible to recover all the electric energy generated during braking because the braking operation may be required at any time depending on the driving conditions, and the braking torque generally varies in a wide range. range. A converting resistor is therefore provided to deal with the situation when the braking energy is too excessive to be recovered. The resistor is connected to the electrical output of the machine through a switching circuit so as to convert the excessive electrical energy dissipated as thermal energy when a high braking torque is provided within a short period.

The converting resistor is adapted to be automatically connected to the electrical output when the terminal voltage of the DC power source reaches a predetermined voltage (for example, 120%) which is greater than the nominal terminal voltage thereof, so that the control of the conversion of the braking energy by the resistor is independent of the negative feedback control.

When the two switches mentioned above are provided which are operable by the driver, the correct driving operation can be carried out by supplying different slips in the positive and negative directions respectively to the multiphase squirrel cage induction machine according to the manipulation of the driver. This mechanism may be provided with a circuit which receives input information from the key start switch of the internal combustion engine and with a program circuit which generates the control reference for supplying a rotating magnetic field at an extremely low speed suitable for starting the internal combustion engine to the multiphase squirrel cage induction machine according to the input information from the key start switch. The multiphase squirrel cage induction machine may also be used as a motor for starting the internal combustion engine.

The multiphase squirrel cage induction machine and the inverter circuit may have higher output voltages to step down the multiphase output current, but the direct current conventionally mounted on automobiles is of remarkably low voltage. In order to match such a low voltage current to the output voltage of the inverter circuit, it is preferable to use a step-up chopper and to provide a reactor type step-down chopper whereby the relatively low voltage of the rechargeable battery is converted to or from the terminal voltage on the DC side of the inverter.

The mechanism of this invention is characterized by a detector that detects electrical signals corresponding to the rotational speed of the crankshaft, and a controller that controls the essential resistance value of the resistor to a larger value as the rotational speed detected by the detector increases.

The control device preferably comprises a switching semiconductor circuit in series with the resistor and a switch control device which transmits periodic control signals to the switching semiconductor circuit. The switching control device preferably comprises a circuit which can change the duty cycle of the control signals in accordance with the output of the detector, while the detector preferably comprises a circuit which detects changes in the electrical current flowing through the resistor in accordance with electrical signals corresponding to the temperature of the resistor. The control device is preferably structured in a manner that only when the detector output exceeds a predetermined level is the equivalent value of the resistor controlled to increase to a higher value.

The mechanism according to this invention preferably comprises a temperature detector which detects electrical signals corresponding to the temperature of the above-mentioned resistor, and a controller which controls the essential value of the resistor to a lower level when the temperature of the resistor increases according to the output of the detector.

It is preferred that the control device comprises a switching semiconductor circuit connected in series with the resistor and a switching controller which transmits periodic ON-OFF control signals to the switching semiconductor circuit. The switching controller comprises a circuit which can change the duty cycle of the signals in accordance with the output from the temperature detector. The The temperature detector comprises a circuit which detects changes in the electric current flowing through the resistor in the form of electrical signals corresponding to the temperature of the resistor, and the control device comprises a means which can control the essential values of the resistor in accordance with the output from the detector.

It is further preferred that this mechanism comprises a detector that detects electrical signals in accordance with the temperature of the resistor, and a controller that controls the circulating magnetic field in accordance with the output from the detector so as to increase the voltage generated by the multi-phase squirrel cage induction machine. The controller may comprise means that controls the pulse width of the electrical current to be supplied to the multi-phase squirrel cage induction machine.

The essential value of the resistance should be changed in accordance with the rotational speed of the crankshaft of the internal combustion engine in order to effect electrical braking with high efficiency for a long time over a wide range of rotational speeds. When the rotational speed is low, the resistance value should be small, and as the rotational speed increases, the resistance should become larger. This can be realized by changing the taps of the resistance. However, the means for switching the taps of the resistance requires a number of switching circuits and resistive elements with high thermal and current capacity. This would inconveniently increase the size and weight of the device to be mounted on the motor vehicle. It is therefore preferable to use a circuit having a low-value resistance and a switching semiconductor circuit in series, so that the essential resistance value can be changed by periodically switching the switching semiconductor circuit ON and OFF to change the duty cycle thereof.

It is also preferable to use the output from the speed sensor as electrical signals corresponding to the speed of the crankshaft. According to the output, ON-OFF control signals of variable duty cycle are supplied to the switching semiconductor circuit, so that as the output increases, the essential value of the resistance can be controlled to be set to a larger value. In this way, the matching of the power generator and the load can be improved in the region where the speed is high and the generated voltage is high. This increases the braking torque and accordingly the system can be applied to an electric braking system over a wide range.

The power P dissipated by the resistor is expressed as

P = V²/R

where the resistance value of the resistor is R and the DC voltage of the resistor is V. When the electric power is continuously dissipated by the resistor over a long period of time, the temperature of the resistor rises and the resistance value R also increases. If the resistance value R is controlled to a lower level than the effective value, a high dissipated power can be maintained over a long period of time.

More specifically, the output voltage of the inverter and the electric current of the resistor are monitored so that when the current through the resistor increases in proportion to the voltage of the inverter, the essential resistance of the resistor is controlled to increase. When the electric current decreases due to the heat generated by the resistor itself, even if the voltage remains at the same level, the essential resistance of the resistor is controlled to a lower level.

The rise in temperature of the resistor is most easily detected by monitoring whether the current flowing through the resistor decreases in order to detect the decrease in electrical current corresponding to the increase in temperature.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Fig. 1 is a block diagram of the structure of an embodiment according to this invention.

Fig. 2 is a schematic view showing the mounting position of the multi-phase squirrel cage induction machine used in the embodiment of this invention.

Figs. 3 and 4 are mechanical structural diagrams of the structure of the multi-phase squirrel cage induction machine applied in the embodiment of this invention.

Fig. 5 is an electrical circuit diagram in detail of the embodiment of this invention.

Fig. 6 is a perspective view of the steering wheel and the switches of the embodiment of this invention.

Fig. 7 is a circuit diagram of the DC power source of the embodiment of the invention.

Fig. 8 is a block diagram of another structure of the DC power source of another embodiment of this invention.

Fig. 9 shows the inverter output voltage and braking torque according to the rotation speed in the embodiment of this invention.

Fig. 10 is a block diagram for the structure of the DC power source of the embodiment of this invention.

Fig. 11 shows the inverter output voltage, braking torque, duty ratio and essential resistance value according to the rotational speed of the embodiment of this invention.

Fig. 12 shows the value of resistance and duty cycle according to the temperature of the resistor, and also shows the essential value of resistance according to the duty cycle.

Fig. 13 shows the value of the resistor, the dissipated power and the generated voltage according to the temperature of the resistor.

Fig. 14 is a control model diagram of a switching controller in the embodiment of this invention.

Fig. 15 is a flowchart for the sequence of control in the control mode of the embodiment of this invention.

Fig. 16 is a flow chart for the sequence of control in the running mode of the embodiment of this invention.

Fig. 17 is a flowchart for the sequence of control in an auxiliary drive mode of the embodiment of this invention.

Fig. 18 is a flowchart for the sequence of control in the start mode of the embodiment of this invention.

Fig. 19 is a structural diagram in which another embodiment of this invention is mounted on the front of the internal combustion engine.

Fig. 20 is a structural diagram showing the mounting on the output side of the transmission in another embodiment of this invention.

Fig. 21 is a structural diagram of another embodiment of this invention, wherein the mounting is on the intake side of the rear axle.

Fig. 22 is a structural diagram of another embodiment mounted on the propeller shaft between the transmission and the rear axle.

In the figures, 1 denotes the internal combustion engine, 2: the multiphase squirrel cage induction machine, 3: the battery recharging circuit, 4: the inverter, 5: the inverter control unit, 6: the speed sensor, 7: the capacitor, 11 and 11': resistors, 12: the switching semiconductor circuit, 12': the switching circuit, 13: the detector, 14 and 14': switching control units and 15: the detector for the electric current.

[PREFERRED EMBODIMENTS]

This invention will now be described with reference to an embodiment shown in the accompanying drawings.

Fig. 1 is a block diagram of the electrical structure of the embodiment of this invention. Fig. 2 is a schematic view showing the mounting position of the multi-phase squirrel cage induction machine to be used in the embodiment. Fig. 3 is a view of the mechanical structure of the multi-phase squirrel cage induction machine, partially exploded in a plane parallel to the center of the engine crankshaft. And Fig. 4 is a view showing the mechanical structure of the section along the arrow IV-IV in Fig. 3.

As shown in these figures, a rotor of the induction machine is engaged with the flywheel, while a stator is attached to the flywheel housing.

Since this rotary electric induction machine is a multiphase squirrel cage induction machine, the structure of the rotor is very simple and has no brushes. Compared with the conventional induction type machine, the air gap between the rotor and the stator of the induction machine of this invention is larger, so that the magnetic reluctance between the rotor and the stator does not noticeably affect the braking performance. In other words, the manufacturing accuracy for the air gap between the rotor and the stator is not as stringent as in the inductor type power generators.

The electrical structure of this embodiment will now be described with reference to Fig. 1. The system comprises: a multiphase squirrel cage induction machine 2 whose rotor is directly connected to the internal combustion engine 1, a rechargeable battery 3, an inverter 4 which converts the direct current voltage of the rechargeable battery 3 into alternating current voltage of a frequency suitable for inducing a rotating magnetic field at a speed lower than the speed of axial rotation of the induction machine 2, supplies it to the induction machine and converts alternating current from the induction machine 2 into direct current, and an inverter controller 5 which generates control signals for setting the frequency and voltage of the alternating current side of the inverter 4. The inverter controller 5 comprises means for generating control commands from the driver in accordance with the operating conditions of the motor vehicle.

A speed sensor 6 is provided on the squirrel cage induction machine 2. Signals from the sensor 6 are supplied to the inverter controller 5 and information regarding the state of charge of the rechargeable battery is supplied from the battery 3 as an input.

A capacitor 7 and a switching semiconductor circuit 12 are connected to the output of the inverter and a resistor 11 is connected thereto via the switching semiconductor circuit 12. The resistor 11 dissipates excessive electrical energy when the electrical energy is too large for recovery when generated by braking.

A detector 13 is connected to the switching circuit 3 and the circuit 12 for detecting the output voltage of the inverter 4, while a current detector 15 is provided on the resistor 11 for detecting changes in the electric current. The detector 15 is provided with a switching control circuit 14 which controls the semiconductor switch circuit 12 in accordance with the signals detected by it. The circuit 14 is connected to the detector 13.

The mechanical structure of the multiphase squirrel cage induction machine 2 will now be explained with reference to Figs. 2 to 4.

As shown in Fig. 2, the multiphase squirrel cage induction machine 2 is internally mounted in a flywheel 200 fixed between the internal combustion engine 1 and the transmission 300. More specifically, as shown in Fig. 3, in a space defined by the flywheel housings 215 and 216 of the flywheel 200, there are housed a stator core 211, which stator mainly comprises a stator winding 212 inserted into a slot of the core 211, and a lead wire 213, a rotor core 221 and a rotor mainly comprises a rotor rod 222, inserted into a slot of the core 221, and a retaining ring 224 attached to an end ring 223 of the rod 222. The stator core 211 sits in the stator ring 214, and the stator ring 214 is attached to the flywheel housings 215 and 216. The rotor core 221 in turn is attached to the outer periphery of the flywheel 225, which is driven by the crankshaft 226 of the internal combustion engine 1.

The electrical operation of the embodiment is described below.

The rotor of the induction machine 2 is driven by the crankshaft of the internal combustion engine 1 mounted on a vehicle. When the vehicle is braked, the stator winding of the multiphase generator receives the mechanical energy from the rotating system by discharging it. Squirrel cage induction machine 2 receives a voltage having a frequency suitable for inducing a rotating magnetic field of a speed lower than the speed of the rotor of the induction machine 2 from the inverter 4, which is supplied with DC power from the rechargeable battery 3. This machine 2 converts the mechanical energy of the rotating system into electrical energy, which is fed back into the battery 3 via the inverter 4.

The inverter control unit 5 contains a device that controls the inverter 4, the degree of control depending on the operating conditions of the vehicle.

In cases where a high braking torque is generated in a short period under certain driving conditions, it is difficult to recycle all of the electrical energy generated by the multiphase squirrel cage induction machine 2 to the battery 3. Part of this energy is therefore converted as thermal energy by the resistor 11, the current of which is controlled by the switching semiconductor circuit 12. The switching semiconductor circuit 12 comprises a circuit which monitors the DC terminal voltage and automatically connects the resistor 11 to both terminals of the battery 3 when the terminal voltage exceeds a predetermined level.

Fig. 5 is an electrical circuit diagram showing this embodiment in more detail.

In this embodiment, the multiphase squirrel cage induction machine 2 is three-phase. An inverter 4 connects the rechargeable battery 3 to the multiphase squirrel cage induction machine 2. The negative terminal E of the battery 3 is connected to the common potential of the motor vehicle.

The inverter 4 comprises switching elements Qa, Qb, Qc, Qd, Qe and Qf connected between the positive and negative terminals of the battery 3 and each of the three terminals of the induction machine 2. These switching elements Qa, Qb, Qc, Qd, Qe and Qf comprise transistors and diodes connected in parallel to each other but in opposite directions between the collectors and emitters of the transistors. The inverter 4 comprises an ON-OFF control signal generator PWM, which supplies control signals to the control electrodes of each switching element Qa, Qb, Qc, Qd, Qe and Qf.

The inverter 4 is for the automobile and was specially designed to test this invention, but the basic technology of the same is known. The technique for controlling a rotating magnetic field of the multiphase squirrel cage induction machine according to the rotation of the rotor is an application of a known technique popularly used in AC hoists and cranes.

A speed sensor 6 is mounted on the multiphase squirrel cage induction machine 2 or the internal combustion engine 1 for detecting the revolutions of the crankshaft thereof and for outputting electrical pulse signals. The pulse signals emitted from the speed sensor 6 are converted into an analog signal by means of a digital-to-analog converter DA1 which indicates the speed. The analog signal is supplied to one of the input terminals of the operational amplifier AMP and a control reference corresponding to the slip generated by the digital-to-analog converter DA2 is supplied to another input of the amplifier AMP where these two signals are subtracted or added depending on their polarity. The output from the operational amplifier AMP is fed to the ON-OFF controller PWM as a control signal for the output frequency of the inverter 4. Through these circuit connections, a negative feedback control loop is formed by the multiphase squirrel cage induction machine 2, the speed sensor 6, the digital-analog converter DA1, the operational amplifier AMP and the inverter 4.

The control reference corresponding to the slip is accordingly subtracted or added to the negative feedback control loop. Signals for the control means which generate the slip will now be described. The control means have circuits shown in the lower left part of Fig. 5 comprising: a microprocessor CPU, an interface circuit IO, a torque controller Tq, switches A1 and A2 connected to the accelerator pedal of the vehicle, where switch A1 opens and switch A2 closes when the accelerator pedal is depressed, switches N1 and N2 which are both open in the neutral position of the transmission, switches CL1 and CL2 connected to the clutch pedal and both are open when the clutch pedal is depressed, the first switch S1 is manipulated by the driver, the second switch S2 is manipulated by the driver, the switch KS is connected to the key start switch of the internal combustion engine 1 and to a digital-to-analog converter DA2. The switch S3 is a conventional exhaust brake switch connected to the exhaust brake circuit Ex.

The first switch S1 is for requesting additional acceleration, while the second switch S2 is for requesting electric braking. In this embodiment, these switches S1 and S2 are designed to be operated by a lever L mounted on the control column as shown in Fig. 6. When the lever L is positioned OFF, both switches S1 and S2 are open, and when it is moved to the upper position for acceleration, the switch S1 is closed. Four positions are marked at the lower position for braking, and several contacts, shown at switch S2 of Fig. 5, are closed according to the selected position of the lever L. By using the four braking positions, the driver can select the level of electric braking power.

When the lever L is moved to the upper position for acceleration, the amount of acceleration is determined by the position of the accelerator pedal. The data regarding the position of the pedal are supplied to a terminal T1 in Fig. 5, which transmits them to the torque controller Tq, which transmits control data to the interface 10. The interface IO also receives the output from the temperature sensor H, mounted on the resistor 11, as an input.

This experimental system using the above mechanisms has achieved a braking force of up to 100 HP and a driving force of several tens of HP, the driving force depending on the characteristics of the rechargeable battery. This experimental result sufficiently verifies the viability of the system. In this embodiment, the rotor of the multi-phase squirrel cage induction machine 2 is fixed to the flywheel of the internal combustion engine 1. The diameter of the flywheel housing is approximately 700 mm.

The major components among these parts of the control system for the above embodiment in Fig. 5 are the inverter 4 and the rechargeable battery 3. It is to be noted that a conventional battery for common automobiles or a slightly larger battery can be selected as the rechargeable battery 3. Although the inverter 4 has bulky switch elements Qa, Qb, Qc, Qd, Qe and Qf, the total volume of the inverter of the test system is about 80 liters, which can generate a braking force of about 150 HP. The dimensions were small enough to be mounted on the bottom of the body of a medium-sized truck. The volume can be reduced by future development efforts. The inverter 4 comprises stationary electrical parts without movable elements, for example, switch elements Qa, Qb, Qc, Qd, Qe and Qf, which are capable of being installed at different locations of the vehicle. This makes it possible to construct practical shapes for different types of motor vehicles.

The driving behavior of the system is similar to driving a vehicle with a conventional exhaust braking system and it is verified that a usable driving behavior is sufficiently achieved.

Since the rotating electric machine of this system is of the multiphase squirrel cage induction type, the rotor means is very simple in structure and it is durable and has no frictional parts such as brushes. In the experiment, the gap between the rotor and stator in the system was set to about twice the distance of the conventional inductor type. It was found that the experimental system with the large gap poses no special problems and that even a wider gap is possible. It is therefore found that this invention requires less strict manufacturing accuracy and is therefore very advantageous for mass production. It was also found that the squirrel cage structure generates almost no magnetic noise from the rotor and that the noise of the stator is significantly lower than that of conventional inductor type retarders.

Although in the above embodiment a squirrel cage induction machine with three phases is used, it may be possible to use multiphase machines with a larger number of phases. By increasing the number of phases, the electric current for one phase can be reduced. This is more advantageous for smaller motor vehicles, where parts of the inverter are distributed within different spaces of the vehicle.

The electrical operation and control of the inverter 4 are now described.

When braking power is required for the rotating system, the inverter controller 5 outputs control signals for generating the rotational speed of the magnetic field which is smaller than the mechanical rotational speed of the rotor of the induction machine 2 detected by the sensor 6. At this time, the multiphase squirrel cage induction machine 2 operates as a power generator, and the generated electric energy is converted into DC energy by the inverter 4, and the DC energy is supplied to the rechargeable battery 3. When the braking torque is too high to be absorbed by the battery 3, the terminal voltage of the battery 3 increases to exceed the predetermined level, and the switching semiconductor circuit 12 is closed to connect the terminal of the battery 3 to the resistor 11.

When driving power is required for the rotating system, the inverter control device 5 outputs control signals for generating the rotational speed of the magnetic field which is higher than the mechanical rotation speed of the rotor of the induction machine 2 detected by the sensor 6. At this time, direct current is taken from the rechargeable battery 3. The direct current is converted into multiphase alternating current according to the rotating field by means of the inverter 4 and is supplied to the multiphase squirrel cage induction machine 2.

The greater the difference between the speed of the magnetic rotating field and the axial speed, the greater the braking torque or the driving force. In this embodiment, the ratio of the difference to the speed of the magnetic Rotating field, ie the slip of the multiphase squirrel cage induction machine, limited to within ±-10%.

A description will now be given of the control relating to the charging of the rechargeable battery. The inverter 4 is supplied with control signals from the inverter controller 5 for inducing a rotating magnetic field corresponding to the speed of the rotor on the stator of the induction machine 2. The inverter controller 5 is supplied with the speed data from the sensor 6 and with the data relating to the state of charge of the battery 3. The inverter controller 5 comprises a microprocessor. The inverter controller 5 comprises a means for picking up the operating control signals which change due to manipulation by the driver.

As described above, the inverter 4 can supply power from the DC terminals to the AC terminals, as well as power from the AC terminals to the DC terminals. The inverter can further operate the multiphase squirrel cage induction machine 2 as a multiphase motor by controlling the speed of the rotating magnetic field in accordance with the control signal from the inverter controller 5, and the induction machine 2 transmits driving power to the rotating shaft. Thus, the induction machine 2 works as an auxiliary driving device for the internal combustion engine 1. For this purpose, the electric energy stored in the battery 3 is used.

Conventionally, the charging current for a rechargeable battery of a motor vehicle is supplied by a generator driven by the engine, and charging is continued as long as the engine is running. When the stored energy is consumed by operating the starter motor or other equipment, the charging current to the battery is controlled to reach the fully charged state with respect to the rated capacity in the shortest possible time.

However, in the technique where the energy generated for braking is recycled as electrical energy and used as an auxiliary power for propelling the vehicle, as described above, one cannot effectively recover the braking energy to to improve the fuel efficiency when the rechargeable battery is constantly kept at a fully charged state relative to the rated capacity. On the other hand, if the target capacity for charging is set to one of the low levels relative to the rated capacity, the stored energy is consumed when the starter motor is repeatedly operated as occurs under certain driving conditions.

In this invention, therefore, the target capacity for charging the rechargeable battery is selected to be smaller than the rated capacity under normal conditions. The target capacity must depend on various conditions such as braking performance, driving conditions, rated charging capacity of a rechargeable battery, and temperature. The target capacity may be 50 to 70% of the rated capacity.

When the electric energy recycled and charged increases to exceed the above preset target level, the system issues an alarm and urges the driver to use the auxiliary driving force. Then, electric energy is supplied to the multi-phase squirrel cage induction machine 2 by the driver's manipulation, and its effective use is achieved.

Regarding the information on the state of charge of the rechargeable battery to be supplied to the inverter controller 5, this invention uses a method of monitoring the terminal voltage of the battery for discrimination. This method is not precise, but is useful. To improve accuracy, the system may employ methods to either monitor the density of the battery fluid or to measure and calculate the electrical charge and discharge of the battery.

The system may use a method for reducing the fuel consumption of the internal combustion engine by warning the driver that the charged electricity in the battery is excessive and requires him to use the auxiliary power. Another method that may be used is to integrate into the inverter control unit 5 a microprocessor that receives information that the charged energy exceeds the preselected target level, and which automatically controls the multi-phase squirrel cage induction machine 2 to operate as a motor even during normal driving in accordance with the depressed position of the accelerator pedal.

The control for electric braking and auxiliary acceleration according to the invention is described below.

As shown in Fig. 5, a rechargeable battery 3, the series connection of a resistor 11 and a switching semiconductor circuit 12 are connected to the DC terminals E1 and E2 of the inverter 4. A control device CT1 is connected to the control electrode of the switching semiconductor circuit 12.

In this embodiment, the control device CT1 is independent of the control system including the aforementioned microprocessor CPU1, so that when the voltage between the terminals E1 and E2 exceeds the target level, the semiconductor switch 12 is automatically operated. A temperature sensor H is provided on the resistor 11 which is in series with the semiconductor switch 12, and the output from the sensor H is supplied to the interface circuit 10. When the temperature of the resistor 11 exceeds the preselected value, the slip of the rotating magnetic field can be reduced, thereby reducing the braking torque.

The operating voltage between terminals E1 and E2 is in the range of 300-600 V. In this embodiment, a circuit shown in Fig. 7 is used to adapt the above voltage to the voltage of the battery of 24 V, the conventional battery voltage of larger automobiles. Terminals E1 and E2 in Fig. 7 are connected to terminals E1 and E2 in Fig. 5. Capacitor C1 is connected to terminals E1 and E2. The nominal voltage of battery B is 24 V. Capacitor C2 is connected to battery B. Between the positive terminal of battery B and terminal E1 is a series connection of a reactance L and a diode D2 for suppressing reverse current. Between the connection of reactance L with diode D2 and terminal E2 is connected the collector-emitter circuit of transistor Q2. A collector-emitter circuit of the transistor Q3 is connected in parallel to the diode D2.

As shown in the lower half of Fig. 7, this circuit comprises two comparators CP1 and CP2 and a controller CT2 for supplying a controlling pulse to the transistors Q2 and Q3, designated Dr and Br respectively. The transistor Q2 is used when the induction machine 2 operates as a motor. The transistor Q3 is used when the induction machine 2 operates as a generator. The controller CT2 receives as input the operating data of the first and second switches S1 and S2 respectively, which were described with reference to Fig. 5. The first switch S1 and the second switch S2 are operated by the driver and the first switch S1 is closed for auxiliary acceleration while the second switch S2 is closed for electrical braking.

When the first switch S1 is operated and the multi-phase squirrel cage induction machine 2 operates as a motor, the controller CT2 selects the terminal Dr. By applying a much shorter pulse than the repetition period to the terminal Dr of the transistor Q2, the voltage of the battery B is applied to the reactance L for a short period of time and subsequently a high voltage is generated. The sum of the voltage at the two terminals of the reactance L and the terminal voltage of the battery 3 is supplied to the capacitor C1 through the diode D2. The terminal voltage of the capacitor C1 becomes the DC power source voltage for the multi-phase squirrel cage induction machine 2 when it operates as a motor. The DC power source voltage is compared with the reference voltage Er2 by means of the comparator CP2, and the pulse width and repetition period thereof are adjusted to keep the voltage in the preset range.

When the second switch S2 is operated to make the multiphase squirrel cage induction machine 2 operate as a generator, the control device CT2 selects the terminal Br. At this time, periodic pulses are supplied to the control input terminal Br of the transistor Q3 to intermittently operate the transistor Q3. This intermittent operation forms an intermittently closed Loop between the capacitor C1 (terminals E1 and E2), capacitor C2, the reactance L and the transistor Q3 so as to store energy in the reactance L. When the energy in the reactance L increases and the terminal voltage of the reactance L becomes larger than the terminal voltage of the battery B, a closed loop in the opposite direction of the current is formed between the reactance L, the battery B and the diode D3 to allow electric current to flow and charge the battery B. The terminal voltage of the battery B and the terminal voltage of the capacitor C2 are compared with the reference voltage Er1 by the comparator CP1, and the pulse width and the repetition period thereof are adjusted to keep the voltage in the preset range.

The operating modes of the mechanism can be roughly classified into three groups;

(1) Generator mode (the induction machine works as a generator)

(2) Drive mode (the induction machine works as a motor)

(3) Stop mode (the rotor stops)

In the generator mode (1), the multiphase squirrel cage induction machine 2 operates as a power generator, and this mode is further divided into two categories;

(1)a Braking mode

(1)b Running mode.

In braking mode (1)a, which is the mode where the vehicle is braked, a large amount of energy is generated by the multiphase squirrel cage induction machine 2, part of which is recovered by the battery B, but most of which is dissipated via the resistor 11. In this mode (1)a, the slip of the rotating magnetic field to be supplied to the induction machine 2 is controlled to remain negative at a high level. This mode is determined by the driver closing the second switch S2. It is controlled to generate an increasingly larger braking torque by closing the contacts of the second switch S2 in successive steps.

The running mode (1)b is the mode for normal running of the car, where a relatively small amount of energy is generated by the multiphase squirrel cage induction machine 2, gradually but continuously charging the rechargeable battery B. In this mode, the slip of the rotating magnetic field to be supplied to the induction machine 2 is controlled to be negative and small. When the first and second switches are open, the control mode is automatically set to this mode.

The drive mode (2) can be further divided into

(2)a Auxiliary drive mode and

(2)b Start mode.

In mode (2)a, the induction machine 2 operates as a motor to supply additional driving power to the internal combustion engine 1 when additional engine torque is required for starting or for climbing a hill. This is realized by controlling the slip of the induction machine to become positive via the driver's operation of the first switch S1. The slip is controlled in accordance with the value generated by the torque control unit Tq corresponding to the pressure exerted on the accelerator pedal. In this mode, part of the vehicle's driving torque is supplied by the induction machine.

In the starting mode (2)b, when the internal combustion engine 1 is operated from the stopped state, the rotational power is supplied from the induction machine 2 instead of the conventional DC starter motor. For this purpose, a low-speed magnetic field such as about 200 rpm is supplied to the induction machine 2. This eliminates the need for a starter motor, pinion gear, magnetic switch and other components normally required for starting.

In the above generator mode (1), the system supplies the rotating magnetic field at a speed lower than the current speed of the rotor, or a negative slip for the induction machine 2. The induction machine 2 operates as a generator, and the electric current for the rotating magnetic field is supplied via the Transistor parts of the switching elements Qa, Qb, Qc, Qd, Qe and Qf. The electrical energy generated by the induction machine 2 is recycled to the battery 3 via the diode parts of the switching elements Qa, Qb, Qc, Qd, Qe and Qf. When a high braking torque is temporarily required and when the energy generated becomes too large to be recovered, the terminal voltage of the battery 3 increases and the semiconductor switch 12 closes to convert the energy from the resistor 11 into thermal energy. When the thermal energy remains at a high value in the resistor, the slip of the circulating magnetic field is controlled by the output from the temperature sensor H to decrease and the braking force is reduced to keep the system within a safe operating range.

In the above drive mode (2), the induction machine 2 obtains a positive slip, which makes the speed of the rotating magnetic field greater than that of the rotor of the induction machine 2. This makes the induction machine 2 a motor that transmits rotational power to the crankshaft of the machine 1.

It will now be described how the resistance value of the resistor 11, which converts thermal energy in the system, is controlled.

Various tests were carried out on the above embodiment, and the inventors found that when the vehicle is running beyond a certain high speed of the engine and when the system is operated in the braking mode, the braking torque suddenly becomes extremely low. The inventors studied this phenomenon in detail and found that it can be avoided by selecting the value of the converting resistor 11. More specifically, when the induction machine is operated as a generator and when its speed is very high, the output voltage is suddenly reduced in the region of a smaller magnetic field to thereby lower the output power from the generator. That is, in this situation, the converted power (V²/R) in the low value of the resistor 11 exceeds the output of the generator. To avoid this, the value of the resistor 11 should be changed according to the speed at the time of braking. Fig. 5 shows an embodiment of the control circuit to achieve this purpose.

Fig. 8 is a block diagram showing an embodiment of a circuit that detects the rotational speed of the crankshaft and controls the resistance value of the resistor 11. The circuit can be constructed as follows: inserting a resistor 11' having ON-OFF switches SW1, SW2 and SW3 that can select resistance values of R1, R2 and R3, respectively, between the terminals E1 and E2 of the inverter 4, connecting a switch controller 14' that controls the ON-OFF switches SW1, SW2 and SW3, and connecting a detector 13 that detects the output voltage and transmits a signal to the controller 14'.

The inventors have conducted various tests on the above embodiment and found that the controllable range can be expanded by switching the ON-OFF switches SW1, SW2 and SW3 in accordance with the signals detected in relation to the rotational speed.

Fig. 9(a) and 9(b) show the output voltage and braking torque of the inverter in relation to the speed. As shown in Fig. 9(a), the resistance is increased as R3, R2 and R1 as the speed increases. In this way, the inverter output voltage can be maintained at a substantially constant value. Moreover, although the braking torque decreases slightly as the speed increases, the braking torque remains at a practically sufficient level. Accordingly, it has been found that the resistance value should be changed in order to be able to perform braking over a wide range.

After further research, the inventors discovered a better method according to which the duty ratio (the ratio between the time the switch is ON versus the ON-OFF period) for controlling the semiconductor switch is changed when the output voltage from the inverter 4 exceeds a predetermined level and the essential value of the resistor 11 can be effectively changed.

Fig. 10 is a block diagram showing the structure of this circuit with terminals E1 and E2 connected to terminals E1 and E2 of Fig. 5. In this embodiment, the circuit comprises: a capacitor 7 connected to terminals E1 and E2 of inverter 4, a low-value resistor 11 to which an electric current generated in the stator winding of induction machine 2 is supplied via inverter 4, a semiconductor switch 12 connected between resistor 11 and inverter 4 for switching the circuit, a detector 13 which detects the applied voltage from inverter 4, a switch controller 14 which controls the effective value of resistor 11 to increase as the output detected by circuit 13 and speed sensor 6 increases, and an electric current detector 15 provided on resistor 11 which detects the changes in electric current and outputs detection signals to switch controller 14.

The circuit of the rechargeable battery 3 includes the rechargeable battery 31, a reactance 32, a semiconductor switch 33 and a control device 34.

The operation of the system of the above structure will now be described. The description will be made primarily with reference to the control of the resistor 11 by detecting the voltage from the inverter 4.

When the rotating magnetic field of a speed corresponding to a generator is supplied to the stator winding of the multiphase squirrel cage induction machine 2, the shaft of which is coupled to the crankshaft of the machine 1, alternating current is generated in the stator winding. This alternating current is converted into direct current by the inverter 4 and is applied to the terminals E1 and E2.

The detector 13 detects the voltage and transmits a signal to the switch controller 14. When the detected output voltage exceeds the predetermined level, the switch controller 14 controls the resistor 11 by transmitting ON-OFF control signals to the semiconductor switch 12 to increase the effective value of the resistor 11.

Figs. 11(a), 11(b), 11(c) and 11(d) show the relationship between the rotational speed of the crankshaft of the engine 1 and the DC voltage output, the braking torque, the duty ratio and the effective Resistance value of inverter 4.

As shown in Fig. 11, as the rotation speed of the engine 1 increases from zero to a certain value of the rotation speed Nc1, the braking torque decreases as indicated by the dashed lines in Fig. 11(b). When the rotation speed reaches from zero to the point Nc2 which is slightly lower than Nc1, the detector 13 detects the corresponding output voltage Vc and transmits the detection signal to the switch controller 14. In accordance with the detection signals, the switch controller 14 transmits ON-OFF commands to the semiconductor switch 12. As a result, the duty ratio of the semiconductor switch 12 decreases in pursuit of the increase in rotation speed, and the ON-OFF control signals with the duty ratio reduced as shown in Fig. 11(c) are transmitted to the semiconductor switch 12.

As a result of the operation of the semiconductor switch 12 according to the ON-OFF control signal, the effective resistance value of the resistor 11 increases as shown in Fig. 11(d). This improves the matching between the generator and its load in the region where the rotation speed is high. And this improvement broadens the application range of the electric brake for this mechanism.

The inventors have further found that a response delay occurs when the control is performed with the detected output of the inverter DC voltage alone. Therefore, the rotational speed of the engine 1 detected by the sensor 6 is supplied to the controller in advance, and an auxiliary control or a duty control according to the rotational speed is carried out, as shown in Fig. 11(c). After the inverter DC voltage is detected, the control pattern is corrected by the aforementioned ON-OFF control. This further extends the range of stable braking torques.

The results of the various tests have further revealed another problem, although this problem is less important than the above. When the electric braking is applied continuously for a long time, the temperature of the resistor 11 rises and thus increases its resistance, which at the same time gradually lowers the braking torque. This problem can be substantially solved by using a resistor having a lower temperature coefficient, but it is difficult in practice to obtain an inexpensive resistor having a low temperature coefficient. Therefore, the effective resistance value of the resistor 11 should be lowered by using the above-mentioned circuit when it is used for braking for a long period of time.

For this purpose, the inventors have attempted to control the effective value of the resistor 11 by detecting the electric current flowing through the resistor 11. In this method, the effective value is controlled as the current becomes smaller in comparison with the DC voltage applied to the resistor. The inventors have also attempted another method to control the effective value of the resistor 11 by providing a temperature sensor to the resistor 11. In this method, the control is carried out when the output from the sensor shows a temperature higher than a predetermined value.

When braking is continued and the conversion of electric power is carried out for a long period of time, the temperature of the resistor 11 rises. The detector 15 detects the temperature rise in the resistor 11 in the form of electric current and transmits the detector output to a switch controller 14. The switch controller 14 supplies ON-OFF control signals which change the duty cycle to the semiconductor switch 12 so that the effective value of the resistor 11 can be maintained at a low value.

Fig. 12(a) shows the relationship between the temperature and the resistance value, Fig. 12(b) the relationship between the temperature and duty ratio, and Fig. 12(c) the relationship between the duty ratio and the effective resistance value.

When the temperature of the resistor 11 increases, the resistance value increases as shown by the dashed line in Fig. 12(a), and the electric power converted into thermal energy by the resistor 11 decreases. The duty ratio, on the other hand, is controlled to increase with the temperature increase as shown in Fig. 12(b). The effective resistance value decreases with the increase of the duty cycle, as shown in Fig. 12(c).

The increase in temperature of the resistor 11 is detected as electrical signals by the detector 15 and these signals are transmitted to the switch controller 14 so that an ON-OFF control signal is transmitted to the semiconductor switch 12 for increasing the duty ratio and the resistance value is substantially lowered as shown by the solid line in Fig. 12(a). This enables the realization of a large electric power for a long time so as to maintain the braking torque.

The inverter 4 can also be controlled with electrical signals which detect the temperature increase of the resistor 11 in the following manner. In Fig. 1, when the induction machine 2 operates as a generator, alternating current is generated in the stator winding of the induction machine. It is converted into direct current by the inverter 4 and applied to the resistor 11 for the conversion of electrical power. If the conversion of electrical power continues for a long time, the temperature of the resistor 11 rises. The detector 15 detects the temperature increase of the resistor 11 from its electrical current and transmits the detected output to the inverter controller 5. The inverter controller 5 can control the pulse width to increase the output voltage of the inverter. The inverter controller 5 can also control the speed of the magnetic field of the induction machine to increase the output voltage of the inverter.

Fig. 13(a), 13(b) and 13(c) show the relationship of temperature increase with resistance value (R), dissipated power (P) and generated voltage (V).

When the temperature in the resistor 11 increases as shown in Fig. 13(a), the resistance value (R) of the resistor 11 increases and the converted electric power decreases as indicated by the dashed line in Fig. 13(b). The detector 15 detects the temperature increase in the resistor 11 in the form of electric signals, and the voltage (V) generated by the inverter 4 is increased by the inverter controller 5 according to the temperature, so as to maintain the power conversion at a high level as shown in the solid line in Fig. 13(b).

The operation and structure of embodiments other than those described above are identical with respect to Figs. 1 and 5. For the sake of simplification, overlapping descriptions have been omitted.

As described above, the control of the resistance value of the resistor 11 involves several factors. It is therefore necessary for the switch controller 14 shown in Fig. 10 to be able to optimally control the resistance value taking into account a number of factors. A control model is shown in Fig. 14 for the embodiment of the switch controller 14. The switch controller 14 is in practice realized by a programmed controller shown in Fig. 14. In the model, the input DC voltage Vdc is monitored by a comparator in the main control system, and when the voltage exceeds the predetermined level (corresponding to the above-mentioned Vc), an ON-OFF control signal is output to bring the DC voltage Vdc into agreement with Vc. The first auxiliary control system is provided where the input speed is monitored and compared with a stored table, and when the speed has reached the predetermined level (corresponding to Nc2 above), an ON-OFF control signal is output. The main control system is connected to the auxiliary control system via an AND circuit.

There is another factor for controlling the temperature rise in the resistor 11. The factor is controlled by issuing control signals when either the input from the temperature sensor (not shown) provided on the resistor 11 or with the detected current through the resistor 11 or alternatively by the method of correcting the control output from the above first auxiliary control system.

To carry out these operations, control programs are prepared for the microprocessor CPU of Fig. 5 as shown in Fig. 15-18 as flow charts. Fig. 15 shows a flow chart in braking mode, Fig. 16 in running mode, Fig. 17 in auxiliary drive mode and Fig. 18 in starting mode. In Fig. 15-, the control by the temperature sensor is or by the current sensor, which compensates for changes in the resistance value.

As shown above, this invention can carry out coordinated control by detecting the rotational speed of the main shaft of the internal combustion engine 1 and the output voltage from the inverter 4 and changing the duty ratio of ON-OFF control signals to be supplied to the semiconductor switch 12 based on the detected output, so that the braking torque can be maintained over a wide range. When power is dissipated for a long time and the temperature in the resistor 11 rises, this invention detects the electric current corresponding to the temperature change and changes the duty ratio of the ON-OFF control signals to be supplied to the semiconductor switch 12, so that the controls over a number of factors are harmonized and the braking torque can be maintained over a long period of time.

The aforementioned embodiment of the invention has a structure in which the rotor of the multi-phase squirrel cage induction machine 2 is mounted on the flywheel that is connected to the crankshaft of the internal combustion engine, and a stator is mounted on the inside of the flywheel housing. However, the mounting position of the induction machine is not limited to the flywheel or the flywheel housing.

Some of the embodiments thereof will be described below. Fig. 19 shows a structure in which the multiphase squirrel cage induction machine 2 is mounted on the front of an internal combustion engine. Although this structure is inferior in that it cannot be mounted on a conventional vehicle chassis, it can provide better balance for the crankshaft and a crankshaft torsion damper can be omitted.

Fig. 20 shows a structure in which the multi-phase squirrel cage induction machine 2 is mounted on the rear portion of the gearbox 300. In this case, the induction machine 2 is not integral with the engine 1, but can be separated by a clutch (not shown) and the gearbox 300. This structure enables the application of braking force even when separated from the internal combustion engine 1, because the structure is integral with the rotation of the axle.

Fig. 21 shows a structure in which the multiphase squirrel cage induction machine 2 is mounted at the input of the rear axle 40. Like the structure according to Fig. 20, this structure can be separated by means of a clutch (not shown) or by means of the gearbox 300, and is therefore not integral with the internal combustion engine 1. The mounting structure to the internal combustion engine is identical to one used for conventional machines, without any necessary changes or additions, except for the change in the length of the propeller shaft.

Fig. 22 shows another structure in which the multi-phase squirrel cage induction machine 2 is mounted on the propeller shaft 30 between the gearbox 300 and the rear axle 40. As in the examples of Figs. 20 and 21, it can be separated by a clutch (not shown) or by the gearbox 300 and is not integral with the internal combustion engine 1. This results in an improved space factor and the capacity to use a large rotating machine.

As mentioned above, even if the installation position of a multi-phase squirrel cage induction machine 2 on the automobile is different, each embodiment can achieve the same effect as stated in the above explanation because the structures and operations are the same.

[INDUSTRIAL APPLICATIONS]

Since the mechanism of this invention comprises a multi-phase squirrel cage inductor, compared with an eddy current type retarder or an inductor type power generator of the prior art, this mechanism is smaller and more durable, less noisy and less sensitive to magnetic flux leakage, thereby generating a stronger braking force. Since the mechanism allows a wider gap between its stator core and rotor core, the manufacturing accuracy can be less accurate. This mechanism is therefore very suitable for mass production of electric braking devices. This mechanism is applicable to various automobiles. including large, medium and small automobiles.

This mechanism is equipped with an inverter means capable of setting frequencies sufficiently to output a frequency corresponding to the rotation speed of the rotating magnetic field of the multiphase squirrel cage inductor and a resistor capable of converting excessive transient electric energy into thermal energy when the braking force is applied, thereby maintaining a high braking force by converting excessive electric energy generated during braking. The mechanism of this invention can be operated as a driving means at a low cost, thereby effectively recycling the energy inevitably generated during braking. This saves fuel.

Furthermore, the invention can find a practical application which can generate powerful braking torques which are effective over long periods of time and over a wide range of speeds.

Claims (23)

1. An electric brake and auxiliary motor mechanism for a motor vehicle having a rotary electric machine (2) coupled to the crankshaft (226) of an internal combustion engine (1) for driving the axle of the vehicle, characterized in that the crankshaft (226) and the rotary shaft of the rotary machine (2) are directly coupled, that the rotary machine (2) is a multiphase squirrel cage induction machine, that an electric means is provided for inducing a rotary magnetic field for the multiphase squirrel cage induction machine (2), and that the mechanism comprises a DC power source including a rechargeable battery (3) and an inverter (4) which supplies a rotary magnetic field to the multiphase squirrel cage induction machine (2), the electric current being supplied from the DC power source, the inverter (4) a frequency adjustment range for enabling outputs at a frequency corresponding to the speed of the rotating magnetic field which is higher than that of the multiphase squirrel cage induction machine (2) and a frequency corresponding to the speed of the rotating magnetic field which is lower than that of the speed but in the same direction. 2. The electric brake and auxiliary motor mechanism for a motor vehicle according to claim 1, wherein the rotor (221 to 224) of the multiphase squirrel cage induction machine (2) is mounted on the flywheel (200) which is in engagement with the crankshaft (226) of the internal combustion engine (1). 3. The electric brake and auxiliary motor mechanism for a motor vehicle according to claim 2, wherein the stator (211, 212) of the multiphase squirrel cage induction machine (2) is mounted within the flywheel housing (215, 216) of the internal combustion engine (1). 4. The electric brake and auxiliary motor mechanism for a A motor vehicle according to claim 1, wherein said inverter means (4) comprises switching elements (Qa . . . Qf) of a complex type connected between the phase terminals of said polyphase squirrel cage induction machine (2) and the positive and negative terminals of said DC power source, and which comprises a parallel circuit of transistors and diodes. 5. The electric brake and assist motor mechanism for a motor vehicle according to claim 1, further comprising a rotation sensor (6) which detects the rotational speed information of the multi-phase squirrel cage induction machine (2) as electrical signals, a control means (14) which generates a control reference when the vehicle is driven, an adder which adds the control reference and the rotational speed information and generates an ON-OFF control signal for the switch elements (Qa . . . Qf), and a DC circuit of a switch circuit (12) connected to both the terminals of the DC power source (3) and a resistor (11) of low resistance. 6. The electric brake and auxiliary motor mechanism for a motor vehicle according to claim 5, wherein the control means (14) for setting the control reference comprises a first switch (S1) which is manipulated by the driver and gives an auxiliary drive command, a second switch (S2) which is manipulated by the driver and gives an auxiliary brake command, and a program controller (CT2) which gives a different positive or negative slip for the multi-phase squirrel cage induction machine (2) by manipulating the first or second switch (S1, S2). 7. The electric brake and assist motor mechanism according to claim 5, wherein the control means (14) providing the control reference comprises a circuit receiving as an input the operating data for an ignition key switch (KS) of the internal combustion engine (1), while the program circuit (CT2) includes a means providing a rotating magnetic field suitable for actuating the internal combustion engine (1) to the multi-phase squirrel cage induction machine (2) based on the operating data to output the control reference. 8. The electric brake and assist motor mechanism for a motor vehicle according to claim 5, wherein the DC power source (3) comprises a rechargeable battery (31) having a rated voltage lower than the control voltage of the DC power source, a step-up chopper (Q2) and a step-down chopper (Q3) of a reactor type connected to the rechargeable battery (31). 9. The electric brake and assist motor mechanism for a motor vehicle according to claim 5, wherein the switch circuit (12) comprises a switching circuit means which automatically closes when the terminal voltage of the DC power source (3) reaches a predetermined voltage which exceeds the control voltage thereof. 10. The electric brake and assist motor mechanism for a motor vehicle as claimed in claim 1, further comprising means (34) for maintaining the rechargeable battery (31) at a predeterminable target level that is less than its rated capacity. 11. The electric brake and assist motor mechanism for a motor vehicle according to claim 10, wherein the preset target level is 50 to 70% of the rated capacity thereof. 12. The electric brake and assist motor mechanism for a motor vehicle according to claim 5, wherein the system further comprises a detector (14) that detects electrical signals corresponding to the rotational speed of the crankshaft (226), and a controller (14) that increases the essential value of the resistor (11) according to the rotational speed indicated by the detection output from the detector. 13. The electric brake and auxiliary motor mechanism for a A motor vehicle according to claim 12, wherein the controller further comprises a semiconductor switch circuit (12) connected in series with the resistor (11) and a switch controller (14) which periodically supplies ON-OFF control signals to the semiconductor switch circuit (12), and wherein the switch controller (14) comprises a switching circuit which changes the duty cycle of the ON-OFF control signals based on the detection outputs. 14. The electric brake and assist motor mechanism according to claim 13, wherein the detector (14) comprises a switching circuit (13) which detects the voltage applied to the resistor (11) as electrical signals corresponding to the rotational speed of the crankshaft (226) or the terminal voltage of the series connection of the resistor (11) and the semiconductor switching circuit (12). 15. The electric brake and assist motor mechanism for a motor vehicle according to any one of claims 12 to 14, wherein the controller (14) controls the effective value of the resistor (11) according to the detection output from the detector (13). 16. The electric brake and assist motor mechanism for a motor vehicle according to claim 5, wherein the system further comprises a detector (15) that detects electrical signals corresponding to the temperature of the resistor (11) and a controller (14) that controls the effective value of the resistor (11) to a low value when the resistance increases. 17. The electric brake and assist motor mechanism for a motor vehicle according to claim 16, wherein the controller comprises a semiconductor switch (12) connected in series with the resistor (11) and a switch controller (14) which periodically supplies ON-OFF control signals to the semiconductor switch (12), the switch controller (14) comprising a circuit which changes the duty ratio of the ON-OFF control signals according to the detection output. 18. The electric brake and assist motor mechanism for a motor vehicle according to claim 17, wherein the detector (15) comprises a circuit which detects changes in the electric current flowing through the resistor (11) as electric signals corresponding to the temperature of the resistor (11). 19. The electric brake and assist motor mechanism for a motor vehicle according to any one of claims 16 to 18, wherein the switch controller (14) comprises means for controlling the essential value of the resistance (11) only when the detection output from the detector exceeds a predetermined level. 20. The electric brake and assist motor mechanism for a motor vehicle according to claim 5, wherein the system further comprises a detector (15) that detects electric signals corresponding to the temperature of the resistor (11), and a controller (5) that controls the direct current of the inverter (4) according to the detection output of the detector (15). 21. The electric brake and assist motor mechanism for a motor vehicle according to claim 20, wherein the controller (5) controlling the DC voltage includes means for controlling the pulse width of the electric current supplied to the multiphase squirrel cage induction machine (2). 22. The electric brake and assist motor mechanism for a motor vehicle according to claim 20, wherein the controller (5) controlling the direct current comprises means for controlling the speed of the rotating magnetic field supplied to the multiphase squirrel cage induction machine (2). 23. An electric brake and auxiliary motor mechanism for a motor vehicle comprising a rotating electric machine (2) connected to the crankshaft (226) of the internal combustion engine (1), which driving the axle of the vehicle, characterized in that the rotating machine (2) is a multi-phase squirrel cage induction machine, that an electrical means is provided for supplying a rotating magnetic field to the multi-phase squirrel cage induction machine (2), that the multi-phase squirrel cage induction machine is coupled directly between the transmission (300) and the rear axle of the vehicle, and that the mechanism comprises a DC power source including a rechargeable battery (3) and an inverter (4) supplying a rotating magnetic field to the multi-phase squirrel cage induction machine (2), the electrical current being supplied by the DC power source, which inverter (4) has a frequency adjustment range to enable output frequencies corresponding to the speed of the rotating magnetic field which are higher than those of the multi-phase squirrel cage induction machine (2) and a frequency corresponding to the speed of the rotating magnetic field which is lower than that of the speed but in the same Direction.